In a prior device, the first rotor is rotatably supported by two supporting plates while the driving coil is inserted into and fixed to the supporting plates. Circuit elements controlling the current to the coil are independently combined as a unit on a printed circuit plate which is mounted on a baseplate whereupon the respective circuit elements are electrically connected with soldered lead wires. Since the circuit unit and the coil are individually set up, the procedure for checking the circuit is extremely troublesome since the circuit must be connected to an equivalent load. Also if the rotor is to be checked before the whole device is assembled this must be done by connecting a dummy circuit to the coil. Furthermore in case the checking is executed in the conventional device, especially in an electric clock and the like, it is necessary after the first rotor is assembled to insert the coil in a direction perpendicular thereto so that the assembly proceeding is painstaking and time-consuming.